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Abstract:

A method for manufacturing complex hollow composite parts with at least
one internal structure formed in situ by laying laminated layers around a
removable mandrel assembled inside the part's inner cavity. The inner
mandrel is made up of two jig plate assemblies aligned in a parallel
manner and space apart where the internal structure is to manufactured.
Each jig plate assembly is made up of at least three jig plates stacked
in an edge-to-edge manner Located on opposite sides of each jig plate
assembly is an elastic envelope filled with spherical objects. When
evacuated, the envelope collapses and relaxes and composite material may
then laid up inside the inner cavity and around the envelopes. When
exposed to a heat, the envelopes expand and in situ and form internal
structures inside surface of the cavity. Each envelope and each jig plate
assemblies can be easily dissembled and reused.

Claims:

1. A method for manufacturing a complex hollow composite part with at
least one internal structure comprising the following steps: a. selecting
a mold with an part cavity suitable for laying up composite laminated
layers; b. selecting at least two inner mandrels to be placed inside said
part cavity and used to form an internal structure made of composite
laminated material, each said inner mandrel being made of at least three
plates aligned edge to edge and sliding engage, at least one said plate
being conical in shape enabling said inner mandrel to collapsed with said
plate is sliding removed from said part; c. applying dry fiber, wet
fiber, pre-preg, film infusion ,laminated material around each said inner
mandrel; d. inserting said inner mandrel covered with dry fiber, wet
fiber, pre-preg, film infusion, laminated material inside said mold
cavity; e. selecting at least one elastomeric envelope filled with
spherical material of different diameter and located inside said part
cavity on opposite sides of said two inner mandrels, when each said
envelope is evacuated said envelops become rigid and expands when heated
and compressed to compress against said inner plate mandrels and against
surrounding laminate composite layers; f. positioning said envelopes on
opposite sides and adjacent to said inner plate mandrels; g. laying up
laminate composite layers around said envelopes and said inner plate
mandrels; h. closing said mold; i. heating and curing said part inside
said mold; and, j. moving said envelope and said inner plate mandrels
from said part.

2. A reusable mold used to make composite parts with an insitu formed
internal structure, comprising: a. a two part mold each with a mold
cavity that when joined together to form a mold cavity for a composite
part; a at least one reuseable mandrel, each said reuseable mandrel made
up of two jig plate assemblies configured to be aligned in a space apart,
parallel manner inside said mold cavity, each said jig plate assembly
made up of a plurality of sliding jig plates that are connected together
in an edge to edge manner; and, c. at least one elastic envelope placed
inside said mold cavity, said envelope configured to expand when a vacuum
is created inside said mold cavity and compress laminate material placed
along the inside surface of said mold cavity and exert a force on said
said jig plate assemblies together and compress composite material
located between said jig plate assemblies.

Description:

[0001] This utility patent application is based on and claims the priority
filing date of U.S. Provisional patent application 61/467,871 filed on
Mar. 25, 2011.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The disclosed embodiments relate to the field of manufacturing
complex structures made of composites that are formed in molds using
compacting molding processes , and more particularly, to such structures
that are hollow and include internal structures.

[0004] 2. Description of the Related Art

[0005] The inventor is a co-inventor of a method of producing structures
of complex shapes of composite materials disclosed in U.S. patent
application Ser. No. 12/296,689, filed on Jun. 3, 2009. The method
discloses the use of a flexible, elastomeric envelope, also called a
bladder, filled with small spherical objects of different diameters that
after undergoing evacuation of air, form a rigid mandrel for laying up
dry fiber, prepreg, or film resin to create composite laminated layers on
the inner cavity of a composite part. During setup, the bladder is made
into a rigid mandrel by filling it with spherical objects and then
evacuating the air inside the bladder to compact the spherical objects.
The bladder is then sealed to maintain a vacuum which forms a compact,
temporary rigid mandrel upon which composite layers can be laid. When the
mold is heated, the bladder located inside the part is filled with
compressed air causing it to expand and evenly apply a uniform,
compaction force to the inside surfaces of the part's interior cavity.
Different envelopes may be used that undergo different amounts of
expansion when heated to produce different shape bladders that form
different wall thicknesses

[0006] After compaction, the part is then allowed to cure under regulated
air or nitrogen pressure. After curing, air is allowed to enter the
envelope causing the envelope t relax and return to its original,
flexible state. The envelope is then removed from the part.

[0007] Many industries use hollow, complex-shaped, lightweight parts made
of composite material that must be precisely manufactured to
pre-determined specifications. Not only must the outer surfaces of parts
be manufactured to the desired specifications, but the inside and
interior walls of the part must be precisely shaped and formed so that
exterior and interior walls in the part have the desired thicknesses. It
is important that sufficient compaction be used to eliminate porosity in
the composite layers. An example of a hollow, complex-shaped, lightweight
part made of composite material is a windmill blade.

[0008] U.S. Pat. No. 7,473,385 discloses a method of manufacturing hollow
windmill blades that includes the use of molds that compact the laminated
layers and the use of infused resin. The blade includes a continuous thin
outer layer that forms an upper and lower blade sections that surround a
hollow cavity. Located inside the hollow cavity is a supporting shear web
that extends between the upper and lower sections of the blade. The upper
and lower sections of the blade has a layered, sandwich construction
comprising an upper fiber layer and a lower fiber layer surrounding an
inner passageway that is filled with infused resin , film infusion or
pre-preg material.

[0009] The shear spar is formed by placing two removable jig plates on
opposite sides of the shear spar and the inside the inner cavity. The two
jig plates are located in the spaces located on opposite sides of the
shear web to be constructed therein to create a compaction force when the
envelope or the bladder is pressurized. The outer surfaces of the two jig
plates are covered by fiber layers that when placed inside the inner
cavity, forms a shear cavity. Located inside the shear cavity may be a
piece of core spacer During manufacturing, liquid resin may be infused
into the shear cavity, which after curing forms the shear web. In some
applications, pre-preg material or film infusion may be used in place of
the liquid resin. Surrounding the fiber layers on the upper and lower
sections is a flexible membrane that surrounds the inner passageway that
surrounds the upper and lower sections to compact the fiber layers and to
force the liquid resin, into the inner passageway and the shear cavity.

[0010] One drawback with the method disclosed in U.S. Pat. No. 7,473,385
is that liquid resin is not infused completely or uniformly into the
inner cavity or the shear cavity. As a result, defects in the part may
occur that make the part unusable. Another drawback with this method is
that it requires the use two different manufacturing
processes--heat/vacuum compaction process and vacuum resin infusion
process. The use of these two processes make setup and teardown time
longer and more difficult.

[0011] What is needed is an improved method for method of manufacturing
hollow composite parts formed by compaction with in situ formed internal
structures thereby creating parts that are manufactured to design
specifications with have fewer defects.

SUMMARY OF THE INVENTION

[0012] At the heart of this invention is the discovery that complex,
structural composite structures made by resin, pre-preg or film infusion
processes, often contain defects and other imperfections in the laminate
layers that result in the part being rejected or needing repair before
being used.

[0013] Also at the heart of the invention is that composite parts made
entirely of heat circulation with air compaction processes produce
laminated layers that after curing are uniform and meet design
specifications.

[0014] Disclosed herein is a method of manufacturing complex, composite
structures, such as a wind turbine blade or mast, that have a hollow
inner cavity geometry not achievable with conventional technologies know
today. The method enables structures to be manufactured that can
integrate, one, two, three or more spars (I beam, H Beam, O channel, or
other geometry). The entire structure is manufactured in-situ and is
monolithic, sandwich type or both.

[0015] The geometry of the core is shaped with a formable and deformable,
elastomeric envelope, made of rubber, silicone, Fluor-silicon, or RTV
material. The shape of the envelope can conform to any desired core
geometry. The envelope can be used with any single or multiple spars or
(I beam, H beam, O Channel and other geometry) in the desired location
requested by the structural design of the part. During use, the envelop
is heat expanded and filled with compressed air to apply different
amounts of compression force according to the fibre used during layup to
achieve the right compaction of the laminate.

[0016] The elastomeric bladder, hereinafter called an envelope, is taught
in U.S. patent application Ser. No. 12/296,689, filed on Jun. 3, 2009,
and now incorporated by reference herein. The envelope, the shape of
which is produced the desired shape of the interior cavity formed in the
part, is placed in a mold. The envelope is first filled with solid
spherical objects. After filling the envelope with the spherical objects,
the air or nitrogen inside the envelope is evacuated that has the effect
of compacting and lumping the spherical objects together. The spherical
objects contained inside the envelope gives the envelope its desired
shape and rigidity to act as a support for the positioning of fabrics
pre-impregnated with resin placed there over. The composite layers are
then layed up around the inside surface of the mold cavity and over the
envelope. When the mold is close, a vacuum is created in the mold cavity
that causes the envelope to also expand. After heating and curing the
resin, pre-preg , or the film infusion for the desired amount of time, a
vacuum relative to the outside air is created. In order to removed the
envelope from the mold and to remove the spherical objects from the
envelope, the envelope must be opened. The envelope and spherical objects
can then be removed.

[0017] In the drawings, the part is a wind turbine blade or mast with at
least one internal support structure, hereinafter known as a shear spar.
The shear spar is formed by laying up composite laminated layers around a
removable mandrel temporarily assembled inside the mold cavity and at the
desired location. The removable mandrel includes two parallel jig plate
assemblies spaced apart inside the part's internal cavity. In the
embodiment described herein, the part is made of laminate material can be
made by resin infusion, pre-preg, film infusion or with thermoplastic
material with long fibers reinforcement. Composite laminate material is
laid up over the inner cavity and inbetween the two jig plates forming an
I-shaped uncured laminated structure. A thin twisted UD tow of fiber or a
thin breaded rope fiber ribbon of composite material, called a noodle or
filler, may be placed in the shear web to eliminate voids that can be
created that lead to internal delimitation on the top and bottom of the
laminated structure.

[0018] Each jig plate assembly is made up of at least three conical jig
plates stacked in an edge-to-edge manner inside the part's inner cavity.
The middle plate includes upper and lower straight edges that converge
towards the opposite closed end of the part. During assembly and
disassembly, the middle jig plate slides freely inward or outward between
the upper and lower jig plates thereby enabling the jib plate assembly to
selectively expand or collapse, respectively.

[0019] A key component of the invention is the envelope discussed above
that is used with the two jib plate assemblies. Once layup is completed,
the top section of the mold is then closed over the lower section of the
mold. The inner cavity is then evacuated and the cure cycle is started
generating heat according the resin system cycle of the material
supplier. As stated above, the air inside the envelope may be
progressively replaced by air or nitrogen gas thereby gradually inflating
the envelope and uniformly compacting the laminate layers. This process
is monitored. The air or the nitrogen gas causes the envelope to expand
evenly and uniformly to compress the laminate layers in all directions.
After the composite laminated layers have cured, the part is removed from
the mold and the elastomeric envelope is opened thereby enabling it to
compress and shirk so that it may be removed from the part's inner
cavity. The middle jig plate on each jig plate is able to slide
longitudinally inbetween the upper and lower jig plates thereby enabling
the entire mandrel to be easily removed from the part.

[0020] When completed, a hollow, laminated composite part is produced with
at least one in situ formed internal shear spar that is made by
compression.

DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 is a cross sectional, side elevation view of a wind turbine
blade part with an inner cavity formed therein and with a single shear
spars formed inside the cavity between two envelopes that press against
one set of removable jig plates located inside the inner cavity.

[0022] FIG. 2 is a cross sectional, side elevation view of a wind turbine
blade part similar to the wind turbine blade shown in FIG. 1, with two
shear spars being inside the inner cavity with three envelopes and two
sets of set of jig plates.

[0023] FIGS. 3 and 4 show horizontal cross sectional plan views of the
wind turbine blades shown in FIGS. 1 and 2, respectively, with the jig
plate assemblies and the envelope removed so that the shear spars that
extend the entire length of the part may be more clearly seen.

[0024] FIG. 5 is a cross sectional, elevation view of a section of the
wind turbine blade showing one replaceable mandrel made up of two jig
plate assemblies spaced apart with fiber layup placed the gap formed
between the two jig plate assemblies.

[0025] FIG. 6 is a cross section of the jig plate showing the conical
shape of the middle jig plate with diagonal side walls that enable the
middle jig plate to be pulled outward and disengaged from the adjacent
upper and lower jig plates thereby enabling the entire jig plate assembly
to be easily disassembled.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0026] Disclosed here in a method for manufacturing a complex shape in
situ, hollow core composite blade or boat mast part 24 with at least one
internal structure, herein called a shear spar 30 formed in situ the
part's inner cavity 27 and simultaneously with the part's outer side
walls 28. As shown in FIGS. 3 and 4, the part 25, 25' is shown for
illustration purposes to be a wind turbine blade. It should be understood
that the method disclosed herein may be used to manufacture other
complex, hollow structures, such as a mast, a pole, and an aircraft wing
or stabilizer made of composite material.

[0027] The method disclosed herein uses the elastomeric bladder,
hereinafter called an envelope 50 that is taught in U.S. patent
application Ser. No. 12/296,689, filed on Jun. 3, 2009, and now
incorporated by reference herein. The envelope 50 is made from an
elastomeric material and filled with a plurality of non-inactivity, free
flowing spherical objects 60 of different or identical diameters. The
envelope 50, the shape of which is preferably produced following the
desired shape of the inner cavity 27 formed in the part 24. During use,
the envelope 50 is placed into the mold cavity 22 and presses against the
laminate material 40, 42 laid up along the inside surface of the mold
cavity 22. When a vacuum is created inside the mold 10, the walls of the
envelope 50 expand and exert a compress force against the inside surfaces
of the laminate material 40, 42.

[0028] As mentioned above, the plurality of spherical objects 60 placed
inside the envelope 50 applied a uniform force against the laminate
layers 40, 42. During assembly, the envelope 50 is then partially
evacuated and sealed. When a vacuum is then created inside the mold
cavity 22, the envelope 50 uniformly expands and evenly presses the
laminate material 40, 42 against the inside surface of the mold cavity
22.

[0029] In the Figs and 4, the part 24, 24' is a wind turbine blade or mast
with one internal shear spar 30 or two shear spars 30, 30' respectively.
Each shear spar 30 or 30' is formed by laying up composite laminated
layer 90 inside a removable mandrel 70 temporarily assembled inside the
mold cavity 22. The removable mandrel 70 includes two parallel jig plate
assemblies 72, 82 spaced apart inside the mold cavity 22. Composite
laminate material 90 is laid up inside the gap formed between the two jig
plates assemblies 72, 82 by forming an laminated, shear spar with an
I-shaped configuration. As shown in FIG. 4, a thin twisted UD tow of
fiber or a thin breaded rope fiber ribbon of composite material 100, also
called a noodle or filler, may be placed in the ends of the shear spars o
eliminate voids that may be created that lead to internal delimitation on
the top and bottom of the laminated structure.

[0030] FIG. 1 shows a two part shell-style mold 10 made up of a top mold
section 12 placed over a lower mold section 16. Formed on each section
12, 16 is a partial mold cavity that when closed form an enclosed, sealed
mold cavity 22. Formed on end of the mold cavity is at least one closable
air inlet/outlet port.

[0031] FIG. 2 is a cross sectional, side elevation view of a wind turbine
blade part 25' similar to the wind turbine blade part 25 shown in FIG. 1,
with two shear spars 30, 30' being formed inside mold cavity 22 with at
least one envelope 50 and a replaceable mandrel 70. Each mandrel 70 is
made up of two jig plate assembles 72, 82. Each jig plate assembly 72, 82
is made up of least three plates, 74, 76, 78 and 84, 86, 88 respectively.
The three plates 74, 76, 88 and 84, 86, 88 are stacked in an edge-to-edge
manner inside the mold cavity 22. The adjacent edges on the adjoining
plates include a sliding `dove tail` profile that enable them to slide
together. The edges of the middle plates 76, 86 and the two inside edges
on the upper and lower plates 74, 78 and 84, 88, respectively, are
straight and diagonally aligned so that the middle plates 76, 86 may
slide freely thereby enabling the jig plate assembly 72,82 to selectively
expand or collapse the jig assembly inner mandrel. Also, formed on each
part 24, is a suitable size opening 26 designed to allow the three jig
plates 74, 76, 78 and 84, 86, 88 to be individually removed from the part
24 after curing.

[0032] To manufacture both parts, 24, 25', a mold 12 with two mold
sections 12, 16 is first selected with a suitable mold cavity 22 formed
between them to manufacture the desired hollow part 25, 25'. Each shear
spar 30,30' is formed by laying up composite laminated layers around two
removable jig plates assemblies 72, 82 that are temporarily assembled
inside the mold cavity 22 and at the desired location. In the embodiment
described herein, the laminate material is resin infusion pre-preg, or
film infusion. Composite laminate material is laid up over top, bottom
and one wide surface of each inner section of the jig plate assembly
thereby forming an I-shape, H shape, L shape ,O shape, Z shape, X shape Y
shape uncured laminated structure when both inner mandrels are placed
inside the part's inner cavity. Wet material can be lay up in the same
way as `pre-preg , dry fiber, film infusion, thermoplastic like "twintex"
commingle material and hybrid fibers, kevelar, carbon, balsa, etc.

[0033] FIG. 5 is a cross section , elevation showing the fiber layup
between the jigs plate assemblies 72, 82, sandwich between the two
separate envelopes or between two sections of a single envelope, the
laminate composite material laid up over their inside surfaces and around
their ends.

[0034] FIG. 6 is a cross section, elevation of the jig plate assemblies
showing three three elongated jig plates stacked end to end and showing
the middle jig plate being removed so that jig plate assembly may
collapse and be removed from the cured part.

[0035] Because the mold, the replaceable mandrel and the envelope 50 are
reusable, multiple parts with exact specifications may be manufactured
quickly and easily. In the embodiment described herein, the part is made
of laminate material can be made by resin infusion, pre-preg, film
infusion or with thermoplastic material with long fibers reinforcement.

[0036] In compliance with the statute, the invention described herein has
been described in language more or less specific as to structural
features. It should be understood, however, that the invention is not
limited to the specific features shown, since the means and construction
shown is comprised only of the preferred embodiments for putting the
invention into effect. The invention is therefore claimed in any of its
forms or modifications within the legitimate and valid scope of the
amended claims, appropriately interpreted in accordance with the doctrine
of equivalents.